Hydrocarbon conversion with an attenuated superactive multimetallic catalytic composite

ABSTRACT

Hydrocarbons are converted by contacting them at hydrocarbon conversion conditions with a novel attenuated superactive multimetallic catalytic composite comprising a combination of a catalytically effective amount of a pyrolyzed rhenium carbonyl component with a porous carrier material containing a uniform dispersion of catalytically effective amounts of a platinum group component, which is maintained in the elemental metallic state during the incorporation and pyrolysis of the rhenium carbonyl component, and of an iron component. In a highly preferred embodiment, this novel catalytic composite also contains a catalytically effective amount of a halogen component. The platinum group component, pyrolyzed rhenium carbonyl component, iron component and optional halogen component are preferably present in the multimetallic catalytic composite in amounts, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. % rhenium, about 0.005 to about 4 wt. % iron and about 0.1 to about 3.5 wt. % halogen. A key feature associated with the preparation of the subject catalytic composite is reaction of a rhenium carbonyl complex with a porous carrier material containing a uniform dispersion of an iron component and of a platinum group component maintained in the elemental state, whereby the interaction of the rhenium moiety with the platinum group moiety is maximized due to the platinophilic (i.e. platinum-seeking) propensities of the carbon monoxide ligands associated with the rhenium reagent. A specific example of the type of hydrocarbon conversion process disclosed herein is a process for the catalytic reforming of a low octane gasoline fraction wherein the gasoline fraction and a hydrogen stream are contacted with the attenuated superactive multimetallic catalytic composite at reforming conditions.

CROSS-REFERENCES TO RELATED DISCLOSURES

This application is a division of my prior, copending application Ser.No. 80,639 filed Oct. 1, 1979 and issued Mar. 17, 1981 as U.S. Pat. No.4,256,608; which in turn is a continuation-in-part of my priorapplication Ser. No. 18,811 filed Mar. 7, 1979 and issued July 1, 1980as U.S. Pat. No. 4,210,524; which in turn is a continuation-in-part ofapplication Ser. No. 833,332 filed Sept. 14, 1977 and issued Aug. 21,1979 as U.S. Pat. No. 4,165,276. All of the teachings of these priorapplications are specifically incorporated herein by reference.

The subject of the present invention is a novel attenuated superactivemultimetallic catalytic composite which has remarkably superioractivity, selectivity and resistance to deactivation when employed in ahydrocarbon conversion process that requires a catalytic agent havingboth a hydrogenation-dehydrogenation function and a carboniumion-forming function. The present invention, more precisely, involves anovel dual-function attenuated superactive multimetallic catalyticcomposite which quite surprisingly enables substantial improvements inhydrocarbon conversion processes that have traditionally used a platinumgroup metal-containing, dual-function catalyst. According to anotheraspect, the present invention comprehends the improved processes thatare produced by the use of the instant attenuated superactiveplatinum-rhenium-iron catalyst system which is characterized by a uniquereaction between a rhenium carbonyl complex and a porous carriermaterial containing a uniform dispersion of an iron component and of aplatinum group component maintained in the elemental metallic state,whereby the interaction between the rhenium moiety and the platinumgroup moiety is maximized on an atomic level. In a specific aspect, thepresent invention concerns a catalytic reforming process which utilizesthe subject catalyst to markedly improve activity, selectivity andstability characteristics associated therewith to a degree notheretofore realized for platinum-rhenium or platinum-rhenium-ironcatalyst systems. Specific advantages associated with use of the presentattenuated superactive platinum-rhenium-iron catalyst system in acatalytic reforming process relative to those observed with theconventional platinum-rhenium or platinum-rhenium-iron catalyst systemsare: (1) Increased ability to make octane at low severity operatingconditions; (2) Substantially enhanced capability to maximize C₅ +reformate and hydrogen production; (3) Augmented ability to expandcatalyst life before regeneration becomes necessary in conventionaltemperature-limited catalytic reforming units; (4) Increased toleranceto conditions which are known to increase the rate of production ofdeactivating coke deposits; (5) Diminished requirements for amount ofcatalyst to achieve same results as the prior art catalyst systems at nosacrifice in catalyst life before regeneration; and (6) Capability ofoperating at increased charge rates with the same amount of catalyst andat similar conditions as the prior art catalyst systems without anysacrifice in catalyst life before regeneration.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the carbonium ion-forming function is thought to beassociated with an acid-acting material of the porous, adsorptive,refractory oxide type which is typically utilized as the support orcarrier for a heavy metal component such as the metals or compounds ofmetals of Groups V through VIII of the Periodic Table to which aregenerally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylation, transalkylation, etc. In many cases, the commercialapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of naphthenes and paraffins, and thelike reactions, to produce an octane-rich or aromatic-rich productstream. Another example is a hydrocracking process wherein catalysts ofthis type are utilized to effect selective hydrogenation and cracking ofhigh molecular weight unsaturated materials, selective hydrocracking ofhigh molecular weight materials, and other like reactions, to produce agenerally lower boiling; more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity, and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used--that is, the temperature, pressure,contact time, and presence of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount of reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity refers to the amount of C₅ + yield,relative to the amount of the charge, that is obtained at the particularactivity or severity level; and stability is typically equated to therate of change with time of activity, as measured by octane number ofC₅ + product and of selectivity as measured by C₅ + yield. Actually thelast statement is not strictly correct because generally a continuosreforming process is run to produce a constant octane C₅ + product withseverity level being continuously adjusted to attain this result; andfurthermore, the severity level is for this process usually varied byadjusting the conversion temperature in the reaction so that, in pointof fact, the rate of change of activity finds response in the rate ofchange of conversion temperatures and changes in this last parameter arecustomarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processesthe conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not assensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity, and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level--C₅ + yield being representativeof selectivity and octane being proportional to activity.

I have now found a dual-function attenuated superactive multimetalliccatalytic composite which possesses improved activity, selectivity andstability characteristics relative to similar catalysts of the prior artwhen it is employed in a process for the conversion of hydrocarbons ofthe type which have heretofore utilized dual-function, platinum groupmetal-containing catalytic composites such as processes forisomerization, hydroisomerization, dehydrogenation, desulfurization,denitrogenization, hydrogenation, alkylation, dealkylation,disproportionation, polymerization, hydrodealkylation, transalkylation,cyclization, dehydrocyclization, cracking, hydrocracking, halogenation,reforming and the like processes. In particular, I have now establishedthat an attenuated superactive multimetallic catalytic composite,comprising a combination of a catalytically effective amount of apyrolyzed rhenium carbonyl component with a porous carrier materialcontaining catalytically effective amounts of a platinum group componentand an iron component, can enable the performance of hydrocarbonconversion processes utilizing dual-function catalysts to besubstantially improved if the platinum group component is relativelyuniformly dispersed throughout the porous carrier material prior tocontact with the rhenium carbonyl reagent; if the oxidation state of theplatinum group component is maintained in the elemental metallic stateprior to, during contact with the rhenium carbonyl reagent, and duringthe subsequent pyrolysis thereof; and if high temperature treatment inthe presence of oxygen and/or water of the resulting reaction product isavoided. A specific example of my discovery involves my finding that anattenuated superactive acidic multimetallic catalytic composite,comprising a halogenated combination of a catalytically effective amountof a pyrolyzed rhenium carbonyl component with a porous carrier materialcontaining a uniform dispersion of catalytically effective amounts of aplatinum group component, which is maintained in the elemental metallicstate during the incorporation and pyrolysis of the rhenium carbonylcomponent and of an iron component, can be utilized to substantiallyimprove the performance of a hydrocarbon reforming process whichoperates on a low octane gasoline fraction to produce a high octanereformate or aromatic-rich reformate. In the case of a reformingprocess, some of the major advantages associated with the use of thenovel multimetallic catalytic composite of the present inventioninclude: (1) acquisition of the capability to operate in a stable mannerin a high severity operation; for example, a low or moderate pressurereforming process designed to produce a C₅ + reformate having an octaneof at least about 100 F-1 clear; (2) increased average activity foroctane upgrading reactions relative to the performance of (a) prior artbimetallic platinum-rhenium catalyst systems as exemplified by theteachings of Kluksdahl in his U.S. Pat. No. 3,415,737 and (b) prior artplatinum-rhenium-iron catalyst systems as shown in the teachings of Bussin his U.S. Pat. No. 3,487,010; and (3) substantially increasedcapability to maximize C₅ + yield and hydrogen production relative tothese prior art catalyst systems. In sum, the present invention involvesthe remarkable finding that the addition of a pyrolyzed rhenium carbonylcomponent to a porous carrier material containing a uniform dispersionof a catalytically effective amount of a platinum group componentmaintained in the elemental metallic state and of an iron component, canenable the performance characteristics of the resulting attenuatedsuperactive multimetallic catalytic composite to be sharply andmaterially improved relative to those associated with the prior artplatinum-rhenium and platinum-rhenium-iron catalyst systems.

It is, accordingly, an object of the present invention to provide anattenuated superactive multimetallic hydrocarbon conversion catalysthaving superior performance characteristics relative to the prior artplatinum-rhenium and platinum-rhenium-iron catalyst systems whenutilized in a hydrocarbon conversion process. A second object is toprovide an attenuated superactive multimetallic acidic catalyst havingdual-function hydrocarbon conversion performance characteristics whichare relatively insensitive to the deposition of coke-forming,hydrocarbonaceous materials thereon and to the presence of sulfurcontaminants in the reaction environment. A third object is to providepreferred methods of preparation of this attenuated superactivemultimetallic catalytic composite which methods insure the achievementand maintenance of its unique properties. Another object is to providean improved platinum-pyrolyzed-rhenium-carbonyl catalyst system havingsuperior selectivity characteristics relative to theplatinum-pyrolyzed-rhenium-carbonyl catalyst system disclosed in myprior application Ser. No. 833,332. Another object is to provide a novelacidic multimetallic hydrocarbon conversion catalyst which utilizes apyrolyzed rhenium carbonyl component to beneficially interact with andselectively promote an acidic catalyst containing an iron component, ahalogen component and a uniform dispersion of a platinum group componentmaintained in the metallic state.

Without the intention of being limited by the following explanation, Ibelieve my discovery that rhenium carbonyl can, quite unexpectedly, beused under the circumstances described herein to synthesize an entirelynew type of platinum-rhenium-iron catalyst system, is attributable toone or more unusual and unique routes to greater platinum-rheniuminteraction that are opened or made available by the novel chemistryassociated with the reaction of a rhenium carbonyl reactant with asupported, uniformly dispersed platinum metal. Before considering indetail each of these possible routes to greater platinum-rheniuminteraction it is important to understand that: (1) "Platinum" is usedherein to mean any one of the platinum group metals; (2) The unexpectedresults achieved with my catalyst systems are measured relative to theconventional platinum-rhenium and platinum-rhenium-iron catalyst systemsand relative to the catalyst system of my prior invention as disclosedin my prior application Ser. No. 833,332; (3) The expression "rheniummoiety" is intended to mean the catalytically active form of the rheniumentity derived from the rhenium carbonyl component in the presentcatalyst system; (4) Metallic carbonyls have been suggested generally inthe prior art for use in making catalysts such as in U.S. Pat. Nos.2,798,051, 3,591,649 and 4,048,110, but no one to my knowledge has eversuggested using these reagents in the platinum-rhenium orplatinum-rhenium-iron catalyst systems, particularly where substantiallyall of the platinum component of the catalyst is present in a reducedform (i.e. the metal) prior to incorporation of the rhenium carbonylcomponent. One route to greater platinum-rhenium interaction enabled bythe present invention comes from the theory that the effect of rheniumon a platinum catalyst is very sensitive to the particle size of therhenium moiety; since in my procedure the rhenium is put on the catalystin a form where it is complexed with a carbon monoxide molecule which isknown to have a strong affinity for platinum, it is reasonable to assumethat when the platinum is widely dispersed on the support, one effect ofthe CO ligand is to pull the rhenium moiety towards the platinum siteson the catalyst, thereby achieving a dispersion and particle size of therhenium moiety in the catalyst which closely imitates the correspondingplatinum conditions (i.e. this might be called a piggy-back theory). Thesecond route to greater platinum-rhenium interaction is similar to thefirst and depends on the theory that the effect of rhenium on a platinumcatalyst is at a maximum when the rhenium moiety is attached toindividual platinum sites, the use of platinophilic CO ligands, ascalled for by the present invention, then acts to facilitate adsorptionor chemisorption of the rhenium moiety on the platinum site so that asubstantial portion of the rhenium moiety is deposited or fixed on ornear the platinum site where the platinum acts to anchor the rhenium,thereby making it more resistant to sintering at high temperature. Thethird route to greater platinum-rhenium interaction is based on thetheory that the active state for the rhenium moiety in therhenium-platinum catalyst system is the elemental metallic state andthat the best platinum-rhenium interaction is achieved when theproportion of the rhenium in the metallic state is maximized; using arhenium carbonyl compound to introduce the rhenium into the catalyticcomposite conveniently ensures availability of more rhenium metalbecause all of the rhenium in this reagent is present in the elementalmetallic state. Another route to greater platinum-rhenium interaction isderived from the theory that oxygen at high temperature is detrimentalto both the active form of the rhenium moiety (i.e. the metal) and thedispersion of same on the support (i.e. oxygen at high temperatures issuspected of causing sintering of the rhenium moiety); since thecatalyst of the present invention is not subject to high temperaturetreatment with oxygen after rhenium is incorporated, maximumplatinum-rhenium interaction is obviously preserved. The final theoryfor explaining the greater platinum-rhenium interaction associated withthe instant catalyst is derived from the idea that the active sites forthe platinum-rhenium catalyst are basically platinum metal crystallitesthat have had their surface enriched in rhenium metal; since the conceptof the present invention requires the rhenium to be laid down on thesurface of well-dispersed platinum crystallites via a platinophilicrhenium carbonyl complex, the probability of surface enrichment isgreatly increased for the present procedure relative to that associatedwith the random, independent dispersion of both crystallites that hascharacterized the prior art preparation procedures. It is of course tobe recognized that all of these factors may be involved to some degreein the overall explanation of the impressive results associated with myattenuated superactive catalyst system. A further fact to be kept inmind is that the conventional platinum-rhenium catalyst systems havenever been noted for an activity improvement (i.e. the consensus of theart is that they give the same activity as the all platinum catalystsystem) but its strong suit has always been very impressive stability;in contrast, my attenuated superactive platinum-rhenium-iron catalystsystem in a hydrocarbon reforming process, for example, gives muchbetter average activity than the conventional platinum-rhenium catalystsystem and, even more surprising, this activity advantage is achievedwithout sacrificing hydrogen and C₅ + selectivity.

Against this background then, the present invention is in oneembodiment, a novel trimetallic catalytic composite comprising acombination of a catalytically effective amount of a pyrolyzed rheniumcarbonyl component with a porous material containing a uniformdispersion of catalytically effective amounts of a platinum groupcomponent, which is maintained in the elemental metallic state duringthe incorporation and pyrolysis of the rhenium carbonyl component, andof an iron component.

In another embodiment, the subject catalytic composite comprises acombination of a catalytically effective amount of a pyrolyzed rheniumcarbonyl component with a porous carrier material containing acatalytically effective amount of a halogen component and a uniformdispersion of catalytically effective amounts of a platinum groupcomponent, which is maintained in the elemental metallic state duringthe incorporation and pyrolysis of the rhenium carbonyl component, andof an iron component.

In yet another embodiment the present invention involves a hydrocarbonconversion catalyst comprising a combination of a pyrolyzed rheniumcarbonyl component with a porous carrier material containing a halogencomponent and a uniform dispersion of a platinum group component, whichis maintained in the elemental metallic state during the incorporationand pyrolysis of the rhenium carbonyl component, and of an ironcomponent, wherein these components are present in amounts sufficient toresult in the composite containing, calculated on an elemental basis,about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5wt. % rhenium, about 0.005 to about 5 wt. % iron, and about 0.1 to about3.5 wt. % halogen.

In still another embodiment, the present invention comprises any of thecatalytic composites defined in the previous embodiments wherein theporous carrier material contains, prior to the addition of the pyrolyzedrhenium carbonyl component, not only a platinum group component and aniron component but also a catalytically effective amount of a componentselected from the group consisting of tin, lead, germanium, cobalt,nickel, cadmium, zinc, tungsten, chromium, molybdenum, bismuth, indium,gallium, manganese, tantalum, uranium, copper, silver, gold, one or moreof the rare earth metals and mixtures thereof.

In another aspect, the invention is defined as a catalytic compositecomprising the pyrolyzed reaction product formed by reacting acatalytically effective amount of a rhenium carbonyl complex with aporous carrier material containing a uniform dispersion of catalyticallyeffective amounts of the platinum group component maintained in theelemental metallic state and of an iron component, and thereaftersubjecting the resulting reaction product to pyrolysis conditionsselected to decompose the resulting rhenium carbonyl component.

An ancillary embodiment of the present invention involves a method ofpreparing any of the catalytic composites defined in the previousembodiments, the method comprising the steps of: (a) reacting a rheniumcarbonyl complex with a porous carrier material containing a uniformdispersion of the platinum group component maintained in the elementalmetallic state of an iron component, and thereafter, (b) subjecting theresulting reaction product to pyrolysis conditions selected to decomposethe resulting rhenium carbonyl component, without oxidizing either theplatinum group or rhenium components.

A further embodiment involves a process for the conversion of ahydrocarbon which comprises contacting the hydrocarbon and hydrogen withthe attenuated superactive catalytic composite defined in any of theprevious embodiments at hydrocarbon conversion conditions.

A highly preferred embodiment comprehends a process for reforming agasoline fraction which comprises contacting the gasoline fraction andhydrogen with the attenuated superactive multimetallic catalyticcomposites defined in any one of the prior embodiments at reformingconditions selected to produce a high octane reformate.

An especially preferred embodiment is a process for the production ofaromatic hydrocarbons which comprises contacting a hydrocarbon fractionrich in aromatic precursors and hydrogen with an acidic catalyticcomposite comprising a combination of a catalytically effective amountof a pyrolyzed rhenium carbonyl component with a porous carrier materialcontaining catalytically effective amounts of a halogen component, aniron component, and a uniform dispersion of a catalytically effectiveamount of a platinum group component, which is maintained in theelemental metallic state during the incorporation and pyrolysis of therhenium carbonyl component. This contacting is performed at aromaticproduction conditions selected to produce an effluent stream rich inaromatic hydrocarbons.

Other objects and embodiments of the present invention relate toadditional details regarding the essential and preferred catalyticingredients, preferred amounts of ingredients, appropriate methods ofcatalyst preparation, operating conditions for use with the novelcatalyst in the various hydrocarbon conversion processes in which it hasutility, and the like particulars, which are hereinafter given in thefollowing detailed discussion of each of the essential and preferredfeatures of the present invention.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silcon carbide, clays, and silicatesincluding those synthetically prepared and naturally occurring, whichmay or may not be acid treated for example, attapulgus clay, china clay,diatomaceous earth, fuller's earth, kaolin, kieselguhr, etc., (3)ceramics, porcelain, crushed firebrick, bauxite; (4) refractoryinorganic oxides such as alumina, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, magnesia, boria, thoria, silica-alumina,silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.;(5) crystalline zeolitic alumino-silicates such as naturally occurringor synthetically prepared mordenite and/or faujasite, either in thehydrogen form or in a form which has been treated with multivalentcations; (6) spinels such as MgAl₂ O₄, FeAl₂ O₄, ZnAl₂ O₄, CaAl₂ O₄, andother like compounds having the formula MO-Al₂ O₃ where M is a metalhaving a valence of 2; and (7) combinations of elements from one or moreof these groups. The preferred porous carrier materials for use in thepresent invention are refractory inorganic oxides, with best resultsobtained with an alumina carrier material. Suitable alumina materialsare the crystalline aluminas known as gamma-, eta-, and theta-alumina,with gamma- or eta-alumina giving best results. In addition, in someembodiments the alumina carrier material may contain minor proportionsof other well known refractory inorganic oxides such as silica,zirconia, magnesia, etc.; however, the preferred support issubstantially pure gamma- or eta-alumina. Preferred carrier materialshave an apparent bulk density of about 0.3 to about 0.8 g/cc and surfacearea characteristics such that the average pore diameter is about 20 to300 Angstroms, the pore volume (B.E.T.) is about 0.1 to about 1 cc/g andthe surface area (B.E.T.) is about 100 to about 500 m² /g. In general,best results are typically obtained with a gamma-alumina carriermaterial which is used in the form of spherical particles having: arelatively small diameter (i.e. typically about 1/16 inch), an apparentbulk density of about 0.3 to about 0.8 g/cc, a pore volume (B.E.T.) ofabout 0.4 cc/g. and a surface area (B.E.T.) of about 150 to about 250 m²/g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere, and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

Another particularly preferred alumina carrier material is synthesizedfrom a unique crystalline alumina powder which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a byproduct from a Zieglerhigher alcohol synthesis reaction as described in Ziegler's U.S. Pat.No. 2,892,858. For purposes of simplification, the name "Ziegleralumina" is used herein to identify this material. It is presentlyavailable from the Conoco Chemical Division of Continental Oil Companyunder the trademark Catapal. This material is an extremely high purityalpha-alumina monohydrate (boehmite) which after calcination at a hightemperature has been shown to yield a high purity gamma-alumina. It iscommercially available in three forms: (1) Catapal SB--a spray driedpowder having a typical surface area of 250 m² /g; (2) Catapal NG--arotary kiln dried alumina having a typical surface area of 180 m² /g;and (3) Dispel M--a finely divided dispersable product having a typicalsurface area of about 185 m² /g. For purposes of the present invention,the preferred starting material is the spray dried powder, Catapal SB.This alpha-alumina monohydrate powder may be formed into a suitablecatalyst material according to any of the techniques known to thoseskilled in the catalyst carrier material forming art. Spherical carriermaterial particles can be formed, for example, from this Ziegler aluminaby: (1) converting the alpha-alumina monohydrate powder into an aluminasol by reaction with a suitable peptizing agent and water and thereafterdropping a mixture of the resulting sol and a gelling agent into an oilbath to form spherical particles of an alumina gel which are easilyconverted to a gamma-alumina carrier material by known methods; (2)forming an extrudate from the powder by established methods andthereafter rolling the extrudate particles on a spinning disc untilspherical particles are formed which can then be dried and calcined toform the desired particles of spherical carrier material; and (3)wetting the powder with a suitable peptizing agent and thereafterrolling particles of the powder into spherical masses of the desiredsize in much the same way that children have been known to make parts ofsnowmen by rolling snowballs down hills covered with wet snow. Thisalumina powder can also be formed in any other desired shape or type ofcarrier material known to those skilled in the art such as rods, pills,pellets, tablets, granules, extrudates and the like forms by methodswell known to the practitioners of the catalyst carrier material formingart. The preferred type of carrier material for the present invention isa cylindrical extrudate having a diameter of about 1/32" to about 1/8"(especially about 1/16") and a length to diameter (L/D) ratio of about1:1 to about 5:1, with a L/D ratio of about 2:1 being especiallypreferred. The especially preferred extrudate form of the carriermaterial is preferably prepared by mixing the alumina powder with waterand a suitable peptizing agent such as nitric acid, acetic acid,aluminum nitrate and the like material until an extrudable dough isformed. The amount of water added to form the dough is typicallysufficient to give a loss on ignition (LOI) at 500° C. of about 45 to 65wt. %, with a value of about 55 wt. % being especially preferred. On theother hand, the acid addition rate is generally sufficient to provideabout 2 to 7 wt. % of the volatile free alumina powder used in the mix,with a value of about 3 to 4% being especially preferred. The resultingdough is then extruded through a suitably sized die to form extrudateparticles. These particles are then dried at a temperature of about 500°to 800° F. for a period of about 0.1 to about 5 hours and thereaftercalcined at a temperature of about 900° F. to about 1500° F. for aperiod of about 0.5 to about 5 hours to form the preferred extrudateparticles of the Ziegler alumina carrier material. In addition, in someembodiments of the present invention the Ziegler alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, iron oxide, cobalt oxide, magnesia, boria, thoria,and the like materials which can be blended into the extrudable doughprior to the extrusion of same. In the same manner crystalline zeoliticaluminosilicates such as naturally occurring or synthetically preparedmordenite and/or faujasite, either in the hydrogen form or in a formwhich has been treated with a multivalent cation, such as a rare earth,can be incorporated into this carrier material by blending finelydivided particles of same into the extrudable dough prior to extrusionof same. A preferred carrier material of this type is substantially pureZiegler alumina having an apparent bulk density (ABD) of about 0.6 to 1g/cc (especially an ABD of about 0.7 to about 0.85 g/cc), a surface area(B.E.T.) of about 150 to about 280 m² /g (preferably about 185 to about235 m² /g,) and a pore volume (B.E.T.) of about 0.3 to about 0.8 cc/g.

A first essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof as afirst component of the attenuated superactive catalytic composite. It isan essential feature of the present invention that substantially all ofthis platinum group component is uniformly dispersed throughout theporous carrier material in the elemental metallic state prior to theincorporation of the rhenium carbonyl ingredient. Generally, the amountof this component present in the form of catalytic composites is smalland typically will comprise about 0.01 to about 2 wt. % of finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 wt. % ofplatinum, iridium, rhodium, palladium or ruthenium metal. Particularlypreferred mixtures of these platinum group metals preferred for use inthe composite of the present invention are: (1) platinum and iridium,(2) platinum and rhodium, and (3) platinum and ruthenium.

This platinum group component may be incorporated into the porouscarrier material in any suitable manner known to result in a relativelyuniform distribution of this component in the carrier material such ascoprecipitation or cogelation, ion-exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlorohodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic, orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentand at least a minor quantity of the preferred halogen component in asingle step. Hydrogen chloride or the like acid is also generally addedto the impregnation solution in order to further facilitate theincorporation of the halogen component and the uniform distribution ofthe metallic components throughout the carrier material. In addition, itis generally preferred to impregnate the carrier material after it hasbeen calcined in order to minimize the risk of washing away the valuableplatinum group compound.

A second essential constituent of the multimetallic catalyst of thepresent invention is an iron component. This component may in general bepresent in the instant catalytic composite in any catalyticallyavailable form such as the elemental metal, a compound like the oxide,hydroxide, halide, oxyhalide, aluminate, or in chemical combination withone or more of the other ingredients of the catalyst. Although it is notintended to restrict the present invention by this explanation, it isbelieved that best results are obtained when the iron component ispresent in the composite in a form wherein substantially all of the ironmoiety is in an oxidation state above that of the elemental metal suchas in the form of iron oxide or iron aluminate or in a mixture thereofand the subsequently described oxidation and reduction steps that arepreferably used in the preparation of the instant catalytic compositeare specifically designed to achieve this end. The term "iron aluminate"as used herein refers to a coordinated complex of iron, oxygen, andaluminum which are not necessarily present in the same relationship forall cases covered herein; a specific example of an iron aluminate isiron spinel (FeAl₂ O₄). This iron component can be used in any amountwhich is catalytically effective, with good results obtained, on anelemental basis, with about 0.005 to about 5 wt. % iron in the catalyst.Best results are ordinarily achieved with about 0.01 to about 1 wt. %iron, calculated on an elemental basis. The preferred atomic ratio ofiron to platinum group metal for this catalyst is about 0.1:1 to about10:1.

This iron component may be incorporated in the catalytic composite inany suitable manner known to the art to result in a relatively uniformdispersion of the iron moiety in the carrier material, such as bycoprecipitation or cogellation or coextrusion with the porous carriermaterial, ion exchange with the gelled carrier material, or impregnationof the porous carrier material either after, before, or during theperiod when it is dried and calcined. It is to be noted that it isintended to include within the scope of the present invention allconvention methods for incorporating and simultaneously uniformlydistributing a metallic component in a catalytic composite and theparticular method of incorporation used is not deemed to be an essentialfeature of the present invention. One preferred method of incorporatingthe iron component into the catalytic composite involves cogelling orcoprecipitating the iron component in the form of the correspondinghydrous oxide during the preparation of the preferred carrier material,alumina. This method typically involves the addition of a suitablesol-soluble or sol-dispersible iron compound such as iron chloride, ironnitrate, and the like to the alumina hydrosol and then combining theiron-containing hydrosol with a suitable gelling agent and dropping theresulting mixture into an oil bath, etc., as explained in detailhereinbefore. Alternatively, the iron compound can be added to thegelling agent. After drying and calcining the resulting gelled carriermaterial in air, there is obtained an intimate combination of aluminaand iron oxide and/or aluminate. Another preferred method ofincorporating the iron component into the catalytic composite involvesutilization of a soluble, decomposable compound of iron to impregnatethe porous carrier material. In general, the solvent used in thisimpregnation step is selected on the basis of the capability to dissolvethe desired iron compound and to hold it in solution until it is evenlydistributed throughout the carrier material without adversely affectingthe carrier material or the other ingredients of the catalyst--forexample, a suitable alcohol, ether, acid and the like solvents. Thesolvent is preferably an aqueous, acidic solution. The iron componentmay thus be added to the carrier material by commingling the latter withan aqueous acidic solution of suitable iron salt, complex, or compoundsuch as iron acetate, iron bromide, iron perchlorate, iron chloride,iron citrate, iron hydroxide, iron fluoride, iron formate, iron iodide,iron lactate, iron malate, iron nitrate, iron oxalate, iron tartrate,iron ammonium citrate, iron ammonium oxalate, iron phosphate, and thelike compounds. A particularly preferred impregnation solution comprisesan acidic aqueous solution of iron chloride or iron nitrate. Suitableacids for use in the impregnation solution are: inorganic acids such ashydrochloric acid, nitric acid, and the like, and strongly acidicorganic acids such as oxalic acid, malonic acid, citric acid, and thelike. In general, the iron component can be impregnated either prior to,simultaneously with, or after the platinum group component is added tothe carrier material. However, excellent results are obtained when theiron component is incorporated into the carrier material during itspreparation and thereafter the platinum group component is added in asubsequent impregnation step after the iron-containing carrier materialis calcined.

It is especially preferred to incorporate a halogen component into theplatinum group metal- and iron-containing porous carrier material priorto the reactions thereof with the rhenium carbonyl reagent. Although theprecise form of the chemistry of the association of the halogencomponent with the catalytic composite is not entirely known, it iscustomary in the art to refer to the halogen component as beingchemically combined with the carrier material or with the platinum groupand/or iron components in the form of the halide (e.g. as the chloride).This combined halogen may be either fluorine, chlorine, iodine, bromine,or mixtures thereof. Of these, fluorine and, particularly, chlorine arepreferred for the purposes of the present invention. The halogen may beadded to the carrier material in any suitable manner, either duringpreparation of the support or before or during or after the addition ofthe platinum group and iron components. For example, the halogen may beadded, at any stage of the preparation of the carrier material or to thecalcined carrier material, as an aqueous solution of a suitable,decomposable halogen-containing compound such as hydrogen fluoride,hydrogen chloride, hydrogen bromide, ammonium chloride, etc. The halogencomponent or a portion thereof, may be combined with the carriermaterial during the impregnation of the latter with the platinum groupand/or iron components, for example, through the utilization of amixture of chloroplatinic acid and hydrogen chloride. In anothersituation, the alumina hydrosol which is typically utilized to form apreferred alumina carrier material may contain halogen and thuscontribute at least a portion of the halogen component to the finalcomposite. For reforming, the halogen will be typically combined withthe carrier material in an amount sufficient to result in a finalcomposite that contains about 0.1 to about 3.5%, and preferably about0.5 to about 1.5%, by weight of halogen, calculated on an elementalbasis. In isomerization or hydrocracking embodiments, it is generallypreferred to utilize relatively larger amounts of halogen in thecatalyst--typically, ranging up to about 10 wt. % halogen calculated onan elemental basis, and more preferably, about 1 to about 5 wt. %. It isto be understood that the specified level of halogen component in theinstant attenuated superactive catalyst can be achieved or maintainedduring use in the conversion of hydrocarbons by continuously orperiodically adding to the reaction zone a decomposablehalogen-containing compound such as an organic chloride (e.g. ethylenedichloride, carbon tetrachloride, t-butyl chloride) in an amount ofabout 1 to 100 wt. ppm. of the hydrocarbon feed, and preferably about 1to 10 wt. ppm.

After the platinum group and iron components are combined with theporous carrier material, the resulting platinum group metal- andiron-containing carrier material will generally be dried at atemperature of about 200° F. to about 600° F. for a period of typicallyabout 1 to about 24 hours or more and thereafter oxidized at atemperature of about 700° F. to about 1100° F. in an air or oxygenatmosphere for a period of about 0.5 to about 10 or more hours orconverts substantially all of the platinum group and iron components tothe corresponding metallic oxides. When the preferred halogen componentis utilized in the present composition, best results are generallyobtained when the halogen content of the platinum group metal- andiron-containing carrier material is adjusted during this oxidation stepby including a halogen or a halogen-containing compound in the air oroxygen atmosphere utilized. For purposes of the present invention, theparticularly preferred halogen is chlorine and it is highly recommendedthat the halogen compound utilized in this halogenation step be eitherhydrochloric acid or a hydrochloric acid producing substance. Inparticular, when the halogen component of the catalyst is chlorine, itis preferred to use a molar ratio of H₂ O to HCl of about 5:1 to about100:1 during at least a portion of this oxidation step in order toadjust the final chlorine content of the catalyst to a range of about0.1 to about 3.5 wt. %. Preferably, the duration of this halogenationstep is about 1 to 5 or more hours.

A crucial feature of the present invention involves subjecting theresulting oxidized, platinum group metal- and iron-containing, andtypically halogen-treated, carrier material to a substantiallywater-free reduction step before the incorporation of the rheniumcomponent by means of the rhenium carbonyl reagent. The importance ofthis reduction step comes from my observation that when an attempt ismade to prepare the instant catalytic composite without first reducingthe platinum group component, no significant improvement in theplatinum-rhenium-iron catalyst system is obtained; put another way, itis my finding that it is essential for the platinum group component tobe well dispersed in the porous carrier material in the elementalmetallic state prior to incorporation of the rhenium component by theunique procedure of the present invention in order for synergisticinteraction of the rhenium carbonyl with the dispersed platinum groupmetal to occur according to the theories that I have previouslyexplained. Accordingly, this reduction step is designed to reducesubstantially all of the platinum group component to the elementalmetallic state and to assure a relatively uniform and finely divideddispersion of this metallic component throughout the porous carriermaterial. Preferably a substantially pure and dry hydrogen stream (bythe use of the word "dry" I mean that it contains less than 20 vol. ppm.water and preferably less than 5 vol. ppm. water) is used as thereducing agent is this step. The reducing agent is contacted with theoxidized, platinum group metal-and iron-containing carrier material atconditions including a reduction temperature of about 450° F. to about1200° F., a gas hourly space velocity (GHSV) sufficient to rapidlydissipate any local concentrations of water formed during the reductionof the platinum group metal oxide, and a period of about 0.5 to about 10or more hours selected to reduce substantially all of the platinum groupcomponent to the elemental metallic state. Once this condition of finelydivided dispersed platinum group metal in the porous carrier material isachieved, it is important that environments and/or conditions that coulddisturb or change this condition be avoided; specifically, I much preferto maintain the freshly reduced carrier material containing the platinumgroup metal under a blanket of inert gas to avoid any possibility ofcontamination of same either by water or by oxygen.

A third essential ingredient of the present attenuated superactivecatalytic composite is a rhenium component which I have chosen tocharacterize as a pyrolyzed rhenium carbonyl component in order toemphasize that the rhenium moiety of interest in my invention is therhenium produced by decomposing a rhenium carbonyl in the presence of afinely divided dispersion of a platinum group metal and in the absenceof materials such as oxygen or water which could interfere with thebasic desired interaction of the rhenium carbonyl component with theplatinum group metal component as previously explained. In view of thefact that all of the rhenium contained in a rhenium carbonyl complex ispresent in the elemental metallic state, an essential requirement of myinvention is that the resulting reaction product of the rhenium carbonylcomplex with the platinum group metal-and iron-loaded carrier materialis not subjected to conditions which could in any way interfere with themaintenance of the rhenium moiety in the elemental metallic state;consequently, avoidance of any conditions which would tend to cause theoxidation of any portion of the rhenium ingredient or of the platinumgroup ingredient is a requirement for full realization of thesynergistic interaction enabled by the present invention. This rheniumcomponent may be utilized in the resulting composite in any amount thatis catalytically effective with the preferred amount typicallycorresponding to about 0.01 to about 5 wt. % thereof, calculated on anelemental rhenium basis. Best results are ordinarily obtained with about0.05 to about 1 wt. % rhenium. The traditional rule for rhenium-platinumcatalyst system is that best results are achieved when the amount of therhenium component is set as a function of the amount of the platinumgroup component also hold for my compositions, specifically, I find thatbest results with a rhenium to platinum group metal atomic ratio ofabout 0.1:1 to about 10:1, with an especially useful range comprisingabout 0.2:1 to about 5:1 and with superior results achieved at an atomicratio of rhenium to platinum group metal of about 1:1 to 3:1.

The rhenium carbonyl ingredient may be reacted with the reduced platinumgroup metal- and iron-containing porous carrier material in any suitablemanner known to those skilled in the catalyst formulation art whichresults in relatively good contact between the rhenium carbonyl complexand the platinum group component contained in the porous carriermaterial. One acceptable procedure for incorporating the rheniumcarbonyl component into the composite involves sublimating the rheniumcarbonyl complex under conditions which enable it to pass into the vaporphase without being decomposed and thereafter contacting the resultingrhenium carbonyl sublimate with the platinum group metal- andiron-containing porous carrier material under conditions designed toachieve intimate contact of the carbonyl reagent with the platinum groupmetal dispersed on the carrier material. Typically, this procedure isperformed under vacuum at a temperature of about 70° to about 250° F.for a period of time sufficient to react the desired amount of rheniumwith the carrier material. In some cases, an inert carrier gas such asnitrogen can be admixed with the rhenium carbonyl sublimate in order tofacilitate the intimate contacting of same with the platinum groupmetal-containing porour carrier material. A particularly preferred wayof accomplishing this rhenium carbonyl reaction step is an impregnationprocedure wherein the platinum group metal-containing porous carriermaterial is impregnated with a suitable solution containing the desiredquantity of the rhenium carbonyl complex. For purposes of the presentinvention, organic solutions are preferred, although any suitablesolution may be utilized as long as it does not interact with therhenium carbonyl and cause decomposition of same. Obviously, the organicsolution should be anhydrous in order to avoid detrimental interactionof water with the rhenium carbonyl complex. Suitable solvents are any ofthe commonly available organic solvents such as one of the availableethers, alcohols, ketones, aldehydes, paraffins, naphthenes and aromatichydrocarbons, for example, acetone, acetyl acetone, benzaldehyde,pentane, hexane, carbon tetrachloride, methyl isopropyl ketone, benzene,n-butylether, diethyl ether, ethylene glycol, methyl isobutyl ketone,diisobutyl ketone and the like organic solvents. Best results areordinarily obtained when the solvent is acetone; consequently, thepreferred impregnation solution is rhenium carbonyl dissolved inanhydrous acetone. The rhenium carbonyl complex suitable for use in thepresent invention may be either the pure rhenium carbonyl itself or asubstituted rhenium carbonyl such as the rhenium carbonyl halidesincluding the chlorides, bromides, and iodides and the like substitutedrhenium carbonyl complexes. After impregnation of the carrier materialwith the rhenium carbonyl component, it is important that the solvent beremoved or evaporated from the catalyst prior to decomposition of therhenium carbonyl component by means of the hereinafter describedpyrolysis step. The reason for removal of the solvent is that I believethat the presence of organic materials such as hydrocarbons orderivatives of hydrocarbons during the rhenium carbonyl pyrolysis stepis highly detrimental to the synergistic interaction associated with thepresent invention. This solvent is removed by subjecting the rheniumcarbonyl impregnated carrier material to a temperature of about 100° F.to about 250° F. in the presence of an inert gas or under a vacuumcondition until no further substantial amount of solvent is observed tocome off the impregnated material. In the preferred case where acetoneis used as the impregnation solvent, this drying of the impregnatedcarrier material typically takes about one half hour at a temperature ofabout 225° F. under moderate vacuum conditions.

After the rhenium carbonyl component is incorporated into the platinumgroup metal- and iron-containing porous carrier material, the resultingcomposite is, pursuant to the present invention, subjected to pyrolysisconditions designed to decompose substantially all of the rheniumcarbonyl material, without oxidizing either the platinum group componentor the decomposed rhenium carbonyl component. This step is preferablyconducted in an atmosphere which is substantially inert to the rheniumcarbonyl such as in a nitrogen or noble gas-containing atmosphere.Preferably this pyrolysis step takes place in the presence of asubstantially pure and dry hydrogen stream. It is of course within thescope of the present invention to conduct the pyrolysis step undervacuum conditions. It is much preferred to conduct this step in thesubstantial absence of free oxygen and substances that could yield freeoxygen under the conditions selected. Likewise it is clear that bestresults are obtained when this step is performed in the total absence ofwater and of hydrocarbons and other organic materials. I have obtainedbest results in pyrolyzing rhenium carbonyl while using an anhydroushydrogen stream at pyrolysis conditions including a temperature of about300° F. to about 900° F. or more, preferably about 400° F. to about 750°F., a gas hourly space velocity of about 250 to about 1500 hr.⁻¹ for aperiod of about 0.5 to about 5 or more hours until no further evolutionof carbon monoxide is noted. After the rhenium carbonyl component hasbeen pyrolyzed, it is a much preferred practice to maintain theresulting catalytic composite in an inert environment (i.e. a nitrogenor the like inert gas blanket) until the catalyst is loaded into areaction zone for use in the conversion of hydrocarbons.

The resulting pyrolyzed catalytic composite may, in some cases, bebeneficially subjected to a presulfiding step designed to incorporate inthe catalytic composite from about 0.01 to about 1 wt. % sulfurcalculated on an elemental basis. Preferably, this presulfidingtreatment takes place in the presence of hydrogen and a suitabledecomposable sulfur-containing compound such as hydrogen sulfide, lowermolecular weight mercaptans, organic sulfides, etc. Typically, thisprocedure comprises treating the pyrolyzed catalyst with a sulfiding gassuch as a mixture of hydrogen and hydrogen sulfide containing about 10moles of hydrogen per mole of hydrogen sulfide at conditions sufficientto effect the desired incorporation of sulfur, generally including atemperature ranging from about 50° F. up to about 1000° F. It isgenerally a preferred practice to perform this presulfiding step undersubstantially water-free and oxygen-free conditions. It is within thescope of the present invention to maintain or achieve the sulfided stateof the present catalyst during use in the conversion of hydrocarbons bycontinuously or periodically adding a decomposable sulfur-containingcompound, selected from the above-mentioned hereinbefore, to the reactorcontaining the attenuated superactive catalyst in an amount sufficientto provide about 1 to 500 wt. ppm., preferably about 1 to about 20 wt.ppm. of sulfur, based on hydrocarbon charge. According to another modeof operation, this sulfiding step may be accomplished during thepyrolysis step by utilizing a rhenium carbonyl reagent which has asulfur-containing ligand or by adding H₂ S to the hydrogen stream whichis preferably used therein.

In embodiments of the present invention wherein the instant attenuatedsuperactive multimetallic catalytic composite is used for thedehydrogenation of dehydrogenatable hydrocarbons or for thehydrogenation of hydrogenatable hydrocarbons, it is ordinarily apreferred practice to include an alkali or alkaline earth metalcomponent in the composite before addition of the rhenium carbonylcomponent and to minimize or eliminate the preferred halogen component.More precisely, this optional ingredient is selected from the groupconsisting of the compounds of the alkali metals--cesium, rubidium,potassium, sodium, and lithium--and the compounds of the alkaline earthmetals--calcium, strontium, barium, and magnesium. Generally, goodresults are obtained in these embodiments when this componentconstitutes about 0.1 to about 5 wt. % of the composite, calculated onan elemental basis. This optional alkali or alkaline earth metalcomponent can be incorporated into the composite in any of the knownways, with impregnation with an aqueous solution of a suitablewater-soluble, decomposable compound being preferred.

Another optional ingredient for the attenuated superactive multimetalliccatalyst of the present invention is a Friedel-Crafts metal halidecomponent. This ingredient is particularly useful in hydrocarbonconversion embodiments of the present invention wherein it is preferredthat the catalyst utilized has a strong acid or cracking functionassociated therewith--for example, an embodiment wherein thehydrocarbons are to be hydrocracked or isomerized with the catalyst ofthe present invention. Suitable metal halides of the Friedel-Crafts typeinclude aluminum chloride, aluminum bromide, ferric chloride, ferricbromide, zinc chloride, and the like compounds, with the aluminumhalides and particularly aluminum chloride ordinarily yielding bestresults. Generally, this optional ingredient can be incorporated intothe composite of the present invention by any of the conventionalmethods for adding metallic halides of this type and either prior to orafter the rhenium carbonyl reagent is added thereto; however, bestresults are ordinarily obtained when the metallic halide is sublimedonto the surface of the carrier material after the rhenium is addedthereto according to the preferred method disclosed in U.S. Pat. No.2,999,074. The component can generally be utilized in any amount whichis catalytically effective, with a value selected from the range ofabout 1 to about 100 wt. % of the carrier material generally beingpreferred.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant attenuated superactivemultimetallic catalyst in a hydrocarbon conversion zone. This contactingmay be accomplished by using the catalyst in a fixed bed system, amoving bed system, a fluidized bed system, or in a batch type operation;however, in view of the danger of attrition losses of the valuablecatalyst and of well known operational advantages, it is preferred touse either a fixed bed system or a dense-phase moving bed system such asis shown in U.S. Pat. No. 3,725,249. It is also contemplated that thecontacting step can be performed in the presence of a physical mixtureof particles of the catalyst of the present invention and particles of aconventional dual-function catalyst of the prior art. In a fixed bedsystem, a hydrogen-rich gas and the charge stock are preheated by anysuitable heating means to the desired reaction temperature and then arepassed into a conversion zone containing a fixed bed of the attenuatedsuperactive multimetallic catalyst. It is, of course, understood thatthe conversion zone may be one or more separate reactors with suitablemeans therebetween to ensure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also important to notethat the reactants may be contacted with the catalyst bed in eitherupward, downward, or radial flow fashion with the latter beingpreferred. In addition, the reactants may be in the liquid phase, amixed liquid-vapor phase, or a vapor phase when they contact thecatalyst, with best results obtained in the vapor phase.

In the case where the attenuated superactive multimetallic catalyst ofthe present invention is used in a reforming operation, the reformingsystem will typically comprise a reforming zone containing one or morefixed beds or dense-phase moving beds of the catalysts. In a multiplebed system, it, is, of course, within the scope of the present inventionto use the present catalyst in less than all of the beds with aconventional dual-function catalyst being used in the remainder of thebeds. This reforming zone may be one or more separate reactors withsuitable heating means therebetween to compensate for the endothermicnature of the reactions that take place in each catalyst bed. Thehydrocarbon feed stream that is charged to this reforming system willcomprise hydrocarbon fractions containing naphthenes and paraffins thatboil within the gasoline range. The preferred charge stocks are thoseconsisting essentially of naphthenes and paraffins, although in somecases aromatics and/or olefins may also be present. This preferred classincludes straight run gasolines, natural gasolines, synthetic gasolines,partially reformed gasolines, and the like. On the other hand, it isfrequently advantageous to charge thermally or catalytically crackedgasolines or higher boiling fractions thereof. Mixtures of straight runand cracked gasolines can also be used to advantage. The gasoline chargestock may be a full boiling gasoline having an initial boiling point offrom about 50° F. to about 150° F. and an end boiling point within therange of from about 325° F. to about 425° F., or may be a selectedfraction thereof which generally will be a higher boiling fractioncommonly referred to as a heavy naphtha--for example, a naphtha boilingin the range of C₇ to 400° F. In some cases, it is also advantageous tocharge pure hydrocarbons or mixtures of hydrocarbons that have beenextracted from hydrocarbon distillates--for example, straight-chainparaffins--which are to be converted to aromatics. It is preferred thatthese charge stocks be treated by conventional catalytic pretreatmentmethods such as hydrorefining, hydrotreating, hydrodesulfurization,etc., to remove substantially all sulfurous, nitrogenous, andwater-yielding contaminants therefrom and to saturate any olefins thatmay be contained therein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment, the charge stock can be a paraffinic stockrich in C₄ to C₈ normal paraffins, or a normal butane-rich stock, or ann-hexane-rich stock, or a mixture of xylene isomers, or anolefin-containing stock, etc. In a dehydrogenation embodiment, thecharge stock can be any of the known dehydrogenatable hydrocarbons suchas an aliphatic compound containing 2 to 30 carbon atoms per molecule, aC₄ to C₃₀ normal paraffin, a C₈ to C₁₂ alkylaromatic, a naphthene, andthe like. In hydrocracking embodiments, the charge stock will betypically a gas oil, heavy cracked cycle oil, etc. In addition,alkylaromatics, olefins, and naphthenes can be conveniently isomerizedby using the catalyst of the present invention. Likewise, purehydrocarbons or substantially pure hydrocarbons can be converted to morevaluable products by using the acidic multimetallic catalyst of thepresent invention in any of the hydrocarbon conversion processes, knownto the art, that use a dual-function catalyst.

In a reforming embodiment, it is generally preferred to utilize theattenuated superactive multimetallic catalytic composite in asubstantially water-free environment. Essential to the achievement ofthis condition in the reforming zone is the control of the water levelpresent in the charge stock and the hydrogen stream which is beingchanged to the zone. Best results are ordinarily obtained when the totalamount of water entering the conversion zone from any source is held toa level less than 50 ppm. and preferably less than 20 ppm. expressed asweight of equivalent water in the charge stock. In general, this can beaccomplished by careful control of the water present in the charge stockand in the hydrogen stream. The charge stock can be dried by using anysuitable drying means known to the art, such as a conventional solidadsorbent having a high selectivity for water, for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm. of water equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm. of water orless and most preferably about 5 vol. ppm. or less. If the water levelin the hydrogen stream is too high, drying of same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° F. to 150° F., wherein a hydrogen-richgas stream is separated from a high octane liquid product stream,commonly called an unstabilized reformate. When the water level in thehydrogen stream is outside the range previously specified, at least aportion of this hydrogen-rich gas stream is withdrawn from theseparating zone and passed through an adsorption zone containing anadsorbent selective for water. The resultant substantially water-freehydrogen stream can then be recycled through suitable compressing meansback to the reforming zone. The liquid phase from the separating zone istypically withdrawn and commonly treated in a fractionating system inorder to adjust the butane concentration, thereby controlling front-endvolatility of the resulting reformate.

The operating conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic, olefin,and paraffin isomerization conditions include: a temperature of about32° F. to about 1000° F. and preferably from about 75° F. to about 600°F., a pressure of atmospheric to about 100 atmospheres, a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1, and an LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst and expressed in units of hr.⁻¹) of about 0.2to 10. Dehydrogenation conditions include: a temperature of about 700°F. to about 1250° F., a pressure of about 0.1 to about 10 atmospheres, aliquid hourly space velocity of about 1 to 40, and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicalhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400° F. to about 900° F., an LHSV ofabout 0.1 to about 10, and hydrogen circulation rates of about 1000 to10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with conventional platinum-rheniumcatalyst systems. In other words, the attenuated superactivemultimetallic catalyst of the present invention allowed the operation ofa continuous reforming system to be conducted at lower pressure (i.e.100 to about 350 psig.) for about the same or better catalyst cycle lifebefore regeneration as has been heretofore realized with conventionalplatinum-rhenium catalysts at higher pressure (i.e. 300 to 600 psig.)

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality platinum-rhenium catalyst of the prior art. Thissignificant and desirable feature of the present invention is aconsequence of the superior activity of the attenuated superactivepyrolyzed multimetallic catalyst of the present invention for theoctane-upgrading reactions that are preferably induced in a typicalreforming operation. Hence, the present invention requires a temperaturein the range of from about 775° F. to about 1100° F. and preferablyabout 850° F. to about 1050° F. As is well known to those skilled in thecontinuous reforming art, the initial selection of the temperaturewithin this broad range is made primarily as a function of the desiredoctane of the product reformate considering the characteristics of thecharge stock and of the catalyst. Ordinarily, the temperature then isthereafter slowly increased during the run to compensate for theinevitable deactivation that occurs to provide a constant octaneproduct. Due to the outstanding initial activity of the catalyst of thepresent invention, not only is the initial temperature requirementlower, but also the average temperature requirement used to maintain aconstant octane product is, for the instant catalyst system,significantly better than for an equivalent operation with a highquality platinum-rhenium catalyst system of the prior art; for instance,a catalyst prepared in accordance with the teachings of U.S. Pat. No.3,415,737. The superior activity, selectivity and stabilitycharacteristics of the instant catalyst can be utilized in a number ofhighly beneficial ways to enable increased performance of a catalyticreforming process relative to that obtained in a similar operation witha platinum-rhenium catalyst of the prior art, some of these are: (1)Octane number of C₅ + product can be increased without sacrificingaverage C₅ + yield and/or catalyst run length. ( 2) The duration of theprocess operation (i.e. catalyst run length or cycle life) beforeregeneration becomes necessary can be increased. (3) C₅ + yield can beincreased by lowering average reactor pressure with no change incatalyst run length. (4) Investment costs can be lowered without anysacrifice in cycle life or in C₅ + yield by lowering recycle gasrequirements thereby saving on capital cost for compressor capacity orby lowering initial catalyst loading requirements thereby saving on costof catalyst and on capital cost of the reactors. (5) Throughput can beincreased significantly at no sacrifice in catalyst cycle life or inC₅ + yield if sufficient heater capacity is available.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10, with a value in the range of about 1 to about 5being preferred. In fact, it is a feature of the present invention thatit allows operations to be conducted at higher LHSV than normally can bestably achieved in a continuous reforming process with a high qualityplatinum-rhenium reforming catalyst of the prior art. This last featureis of immense economic significance because it allows a continuousreforming process to operate at the same throughput level with lesscatalyst inventory or at greatly increased throughput level with thesame catalyst inventory than that heretofore used with conventionalplatinum-rhenium reforming catalyst at no sacrifice in catalyst lifebefore regeneration.

The following examples are given to illustrate further the preparationof the attenuated superactive multimetallic catalytic composite of thepresent invention and the use thereof in the conversion of hydrocarbons.It is understood that the examples are intended to be illustrativerather than restrictive.

EXAMPLE I

A sulfur-free, iron- and chloride-containing alumina carrier materialcomprising 1/16 inch spheres was prepared by: forming an aluminumhydroxy chloride sol by dissolving substantially pure aluminum pelletsin a hydrochloric acid solution, thoroughly mixing ferris chloridehydrate (FeCl₃ ·6H₂ O) with the resulting sol in an amount selected toresult in a final catalyst containing 0.2 wt. % iron, addinghexamethylenetetramine to the resulting iron-containing alumina sol,gelling the resulting solution by dropping it into an oil bath to formspherical particles of an iron-containing alumina hydrogel, aging andwashing the resulting particles and finally drying and calcining theaged and washed particles to form spherical particles of gamma-aluminahavng an iron component uniformly dispersed therein and containingabout, on an elemental basis, about 0.2 wt. % iron and about 0.3 wt. %combined chlorine. Additional details as to this method of preparing thepreferred gamma-alumina carrier material are given in the teachings ofU.S. Pat. No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid andhydrogen chloride was then prepared. The sulfur-free, iron-containingalumina carrier material particles were thereafter admixed with thisimpregnation solution. The amounts of the metallic reagents contained inthis impregnation solution were calculated to result in a finalcomposite containing, on an elemental basis, about 0.375 wt. % platinum.In order to insure uniform dispersion of the platinum componentthroughout the carrier material, the amount of hydrogen chloride used inthis impregnation solution was about 2 wt. % of the alumina particles.This impregnation step was performed by adding the carrier materialparticles to the impregnation mixture with constant agitation. Inaddition, the volume of the solution was approximately the same as thebulk volume of the alumina carrier material particles so that all of theparticles were immersed in the impregnation solution. The impregnationmixture was maintained in contact with the carrier material particlesfor a period of about 1/2 to about 3 hours at a temperature of about 70°F. Thereafter, the temperature of the impregnation mixture was raised toabout 225° F. and the excess solution was evaporated in a period ofabout 1 hour. The resulting dried impregnated particles were thensubjected to an oxidation treatment in a dry air stream at a temperatureof about 975° F. and a GHSV of about 500 hr.⁻¹ for about 1/2 hour. Thisoxidation step was designed to convert substantially all of the platinumand iron ingredients to the corresponding oxide forms. The resultingoxidized spheres were subsequently contacted in a halogen-treating stepwith an air stream containing H₂ O and HCl in a mole ratio of about 30:1for about 2 hours at 975° F. and a GHSV of about 500 hr.⁻¹ in order toadjust the halogen content of the catalyst particles to a value of about1 wt. %. The halogen-treated spheres were thereafter subjected to asecond oxidation step with a dry air stream at 975° F. and a GHSV of 500hr.⁻¹ for an additional period of about 1/2 hour.

The resulting oxidized, halogen-treated, platinum- and iron-containingcarrier material particles were then subjected to a dry reductiontreatment designed to reduce substantially all of the platinum componentto the elemental state and to maintain a uniform dispersion of thiscomponent in the carrier material. This reduction step was accomplishedby contacting the particles with a hydrocarbon-free, dry hydrogen streamcontaining less than 5 vol. ppm. H₂ O at a temperature of about 1050°F., a pressure slightly above atmospheric, a flow rate of hydrogenthrough the particles corresponding to a GHSV of about 400 hr.³¹ 1 andfor a period of about one hour.

Rhenium carbonyl complex, Re₂ (CO)₁₀, was thereafter dissolved in ananhydrous acetone solvent in order to prepare the rhenium carbonylsolution which was used as the vehicle for reacting rhenium carbonylwith the carrier material containing the uniformly dispersed platinumand iron. The amount of this complex used was selected to result in afinished catalyst containing about 0.375 wt. % rhenium derived fromrhenium carbonyl. The resulting rhenium carbonyl-containing solution wasthen contacted under appropriate impregnation conditions with thereduced, platinum- and iron-containing alumina carrier materialresulting from the previously described reduction step. The impregnationconditions utilized were: a contact time of about one half to aboutthree hours, a temperature of about 70° F. and a pressure of aboutatmospheric. It is important to note that this impregnation step wasconducted under a nitrogen blanket so that oxygen was excluded from theenvironment and also this step was performed under anhydrous conditions.Thereafter the acetone solvent was removed under flowing nitrogen at atemperature of about 175° F. for a period of about one hour. Theresulting dry rhenium-carbonyl-impregnated particles were then subjectedto a pyrolysis step designed to decompose the rhenium carbonylcomponent. This step involved subjecting the rhenium carbonylimpregnated particles to a flowing hydrogen stream at a firsttemperature of about 230° F. for about one half hour at a GHSV of about600 hr.⁻¹ and at atmospheric pressure. Thereafter in the second portionof the pyrolysis step the temperature of the impregnated particles wasraised to about 575° F. for an additional interval of about one houruntil the evolution of CO was no longer evident. The resulting catalystwas then maintained under a nitrogen blanket until it was loaded intothe reactor in the subsequently described reforming test.

A sample of the resulting catalytic composite contained, on an elementalbasis, about 0.375 wt. % platinum, about 0.375 wt. % rhenium derivedfrom the carbonyl, about 0.2 wt. % iron and about 1.0 wt. % chlorine.The resulting catalyst is hereinafter referred to as Catalyst A. Forthis catalyst the atomic ratio of iron to platinum was about 1.86:1 andthe atomic ratio of rhenium to platinum was about 1.05:1.

EXAMPLE II

In order to compare the attenuated superactive acidic multimetalliccatalytic composite of the present invention with a platinum-rheniumcatalyst system, in which all of the rhenium component was derived fromthe pyrolysis of rhenium carbonyl, in a manner calculated to bring outthe beneficial interaction of the iron component with this uniquecatalyst system, a comparison test was made between the catalyst of thepresent invention prepared in accordance with Example I, Catalyst A, anda control catalyst, Catalyst B, which is not a prior art catalyst systembut is rather my prior invention as fully disclosed in my copendingapplication Ser. No. 833,332 filed Sept. 14, 1977. Catalyst B wasmanufactured according to the procedure given in Example I except thatthe iron component was excluded therefrom. This control catalystcontained the platinum and rhenium metals in the same amounts as thecatalyst of the present invention; that is, the catalyst contained about0.375 wt. % platinum, about 0.375 wt. % rhenium (derived from pyrolysisof rhenium carbonyl), and about 1.0 wt. % chlorine.

Catalysts A and B were then separately subjected to a high stressaccelerated catalytic reforming evaluation test designed to determine ina relatively short period of time their relatively activity,selectivity, and stability characteristics in a process for reforming arelatively low-octane gasoline fraction. In both tests the same chargestock was utilized and its pertinent characteristics are set forth inTable I.

This accelerated reforming test was specifically designed to determinein a very short period of time whether the catalyst being evaluated hassuperior characteristics for use in a high severity reforming operation.

                  TABLE I                                                         ______________________________________                                        Analysis of Charge Stock                                                      ______________________________________                                        Gravity, API at 60° F.                                                                     59.1                                                      Distillation Profile, °F.                                                     Initial Boiling Point                                                                      210                                                              5% Boiling Point                                                                           220                                                              10% Boiling Point                                                                          230                                                              30% Boiling Point                                                                          244                                                              50% Boiling Point                                                                          278                                                              70% Boiling Point                                                                          292                                                              90% Boiling Point                                                                          316                                                              95% Boiling Point                                                                          356                                                              End Boiling Point                                                                          356                                                       Chloride, wt. ppm.  0.2                                                       Nitrogen, wt. ppm.  0.1                                                       Sulfur, wt. ppm.    0.1                                                       Water, wt. ppm.     10                                                        Octane Number, F-1 clear                                                                          35.6                                                      Paraffins, vol. %   67.4                                                      Aromatics, vol. %   9.5                                                       Naphthenes, vol. %  23.1                                                      ______________________________________                                    

Each run consisted of a series of evaluation periods of 24 hours, eachof these periods comprises a 12-hour line-out period followed by a12-hour test period during which the C₅ + product reformate from theplant was collected and analyzed. The test runs for the Catalysts A andB were performed at identical conditions which comprises a LHSV of 2.0hr.⁻¹, a pressure of 300 psig., a 3.5:1 gas to oil ratio, and an inletreactor temperature which was continuously adjusted throughout the testin order to achieve and maintain a C₅ + target research octane of 100.

Both test runs were performed in a pilot plant scale reforming unitcomprising a reactor containing a fixed bed of the catalyst undergoingevaluation, a hydrogen separation zone, a debutanizer column, andsuitable heating means, pumping means, condensing means, compressingmeans, and the like conventional equipment. The flow scheme utilized inthis plant involves commingling a hydrogen recycle stream with thecharge stock and heating the resulting mixture to the desired conversiontemperature. The heated mixture is then passed downflow into a reactorcontaining the catalyst undergoing evaluation as a stationary bed. Aneffluent stream is then withdrawn from the bottom of the reactor, cooledto about 55° F. and passed to a gas-liquid separation zone wherein ahydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. Aportion of the gaseous phase is then continuously passed through a highsurface area sodium scrubber and the resulting substantially water-freeand sulfur-free hydrogen-containing gas stream is returned to thereactor in order to supply the hydrogen recycle stream. The excessgaseous phase from the separation zone is recovered as thehydrogen-containing product stream (commonly called "excess recyclegas"). The liquid phase from the separation zone is withdrawn therefromand passed to a debutanizer column wherein light ends (i.e. C₁ to C₄)are taken overhead as debutanizer gas and C₅ + reformate streamrecovered as the principal bottom product.

The results of the separate tests performed on the attenuatedsuperactive catalyst of the present invention, Catalysts A, and thecontrol catalyst, Catalyst B, are presented in FIGS. 1, 2 and 3 as afunction of catalyst life as measure in days on oil. FIG. 1 showsgraphically the relationship between C₅ + yields expressed as liquidvolume percent (LV%) of the charge for each of the catalysts. FIG. 2 onthe other hand plots the observed hydrogen purity in mole percent of therecycle gas stream for each of the catalysts. And finally, FIG. 3 tracksinlet reactor temperature necessary for each catalyst to achieve atarget research octane number of 100.

Referring now to the results of the comparison test presented in FIGS.1, 2 and 3 for Catalysts A and B, it is immediately evident that theattenuated superactive multimetallic catalytic composite of the presentinvention substantially outperformed the platinum-rhenium controlcatalyst in the areas of hydrogen production and average C₅ + yield.Turning to FIG. 1, it can be ascertained that the average C₅ +selectivity for Catalyst A was clearly superior to that exhibited forCatalyst B with comparable yield stability. The difference in C₅ + yieldaveraged about 2 vol. % for the duration of the common portion of thetest and represents clear evidence that Catalyst A has much betteryield-octane characteristics than Catalyst B. Hydrogen selectivities forthese two catalysts are given in FIG. 2 and it is clear from the datathat there is a significant increase in hydrogen selectivity thataccompanies the advance of the present invention; I attribute thisincreased hydrogen selectivity to the moderating effect of iron on theincreased metal activity enabled by my unique platinum-rhenium catalystsystem. The data presented in FIG. 3 immediately highlights thesurprising and significant difference in activity between the twocatalyst systems. From the data presented in FIG. 3 it is clear thatCatalyst B was consistently 20° to 25° F. more active than the catalystof the present invention when the two catalysts were run at exactly thesame conditions. Use of an iron component in the case of my catalystsystem, consequently, provides a convenient means to trade-off activityfor C₅ + and hydrogen selectivity and allows my superactiveplatinum-rhenium catalyst system to be moderated or attenuated in orderto adjust the surprising characteristics of this unique catalyst systemto applications where C₅ + yield and hydrogen production are moreimportant than extremely high activity.

In final analysis, it is clear from the data presented in FIGS. 1, 2 and3 for Catalysts A and B that the use of a pyrolyzed rhenium carbonylcomponent to interact with a platinum- and iron-containing catalyticcomposite provides an efficient and effective means for significantlypromoting an acidic hydrocarbon conversion catalyst containing aplatinum group metal when it is utilized in a high severity reformingoperation. It is likewise clear from these results that the catalystsystem of the present invention is a difference in kind rather thandegree from the platinum-rhenium and platinum-rhenium-iron catalystsystems of the prior art.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the hydrocarbonconversion art or in the catalyst formulation art.

I claim as my invention:
 1. A process for converting a hydrocarbon whichcomprises contacting said hydrocarbon at hydrocarbon conversionconditions with a catalytic composite comprising a combination of acatalytically effective amount of a pyrolyzed rhenium carbonyl componentwith a porous carrier material containing a uniform dispersion ofcatalytically effective amounts of a platinum group component, which ismaintained in the elemental metallic state during the incorporation andpyrolysis of the rhenium carbonyl component, and of an iron component.2. A process as defined in claim 1 wherein the platinum group componentis platinum.
 3. A process as defined in claim 1 wherein the platinumgroup component is ruthenium.
 4. A process as defined in claim 1 whereinthe platinum group component is rhodium.
 5. A process as defined inclaim 1 wherein the platinum group component is iridium.
 6. A process asdefined in claim 1 wherein the porous carrier material contains acatalytically effective amount of a halogen component.
 7. A process asdefined in claim 6 wherein the halogen component is combined chlorine.8. A process as defined in claim 1 wherein the porous carrier materialis a refractory inorganic oxide.
 9. A process as defined in claim 8wherein the refractory inorganic oxide is alumina.
 10. A process asdefined in claim 1 wherein the composite contains the components in anamount, calculated on an elemental metallic basis, corresponding toabout 0.01 to about 2 wt. % platinum group metal, about 0.005 to about 5wt. % iron and about 0.01 to about 5 wt. % rhenium.
 11. A process asdefined in claim 6 wherein the halogen component is present therein inan amount sufficient to result in the composite containing, on anelemental basis, about 0.1 to about 3.5 wt. % halogen.
 12. A process asdefined in claim 1 wherein substantially all of the iron component ispresent in an oxidation state above that of the elemental metal.
 13. Aprocess as defined in claim 12 wherein substantially all of the ironcomponent is present as iron oxide or iron aluminate or as a mixturethereof.
 14. A process as defined in claim 1 wherein the metals contentthereof is adjusted so that the atomic ratio of iron to platinum groupmetal is about 0.1:1 to about 5:1 and the atomic ratio of rhenium,derived from the rhenium carbonyl component, to platinum group metal isabout 0.1:1 to about 10:1.
 15. A process as defined in claim 6 whereinthe composite contains, on an elemental basis, about 0.05 to about 1 wt.% platinum group metal, about 0.05 to about 2 wt. % rhenium, about 0.01to about 1 wt. % iron and about 0.5 to about 1.5 wt. % halogen.
 16. Aprocess as defined in claim 1 wherein the composite is prepared by thesteps of: (a) reacting a rhenium carbonyl complex with a porous carriermaterial containing a uniform dispersion of the platinum groupcomponent, maintained in the elemental metallic state, and of the ironcomponent, and thereafter (b) subjecting the reaction product from step(a) to pyrolysis conditions selected to decompose the resulting rheniumcarbonyl component.
 17. A process as defined in claim 16 wherein thepyrolysis step is conducted under anhydrous conditions and in thesubstantial absence of free oxygen.
 18. A process for converting ahydrocarbon as defined in claim 1 wherein the contacting of thehydrocarbon with the catalytic composite is performed in the presence ofhydrogen.
 19. A process as defined in claim 1 wherein said hydrocarboncomprises a gasoline fraction, said hydrocarbon conversion conditionscomprise reforming conditions and wherein said contacting is performedin the presence of hydrogen.
 20. A process as defined in claim 19wherein said reforming conditions include a temperature of about 700° toabout 1100° F., a pressure of about 0 to about 1000 psig, a liquidhourly space velocity of about 0.1 to about 10 hrs.⁻¹ and a mole ratioof hydrogen to hydrocarbon of about 1.1 to about 20:1.
 21. A process asdefined in claim 20 wherein the reforming conditions utilized include apressure of about 50 to about 350 psig.